Low Re Mesh

naveen_010 · April 18, 2012, 04:15

Dear CFD users

In low Re number modelling how does the solver knows, to solve governing equations in all the cells including near wall cells and not to use wall function. I am defining Low Re number k-e turb model with inlet and pressure boundary condition along with standard wall function.

For your information the near wall cells follows the Y+ = 1 and I am having around 12 layers of mesh near the wall.

Thanks in advance.

aerospaceman · April 18, 2012, 04:38

Hi,

As I understand it, you have to select (or not) a solver setting that will employ wall functions.

You are then forcing the code to resolve the boundary layer as opposed of modelling. That is "how it knows.."

Look up your Theory/Users Guide for the package you are using.

Generally however, I'd refine the grid more in order to ensure that everywhere in your domain your Y+ is less than one.

Now don't confuse "Wall Function" with "Wall Damping Functions".

Hope this helps.

naveen_010 · April 18, 2012, 09:40

Dear Aerospaceman

I am using star-cd and in the panel I can choose either stanard wall function,Non-equillbrium or Angelberger for wall function and there is no option to deselect or make it off. with this if i am using a mesh with y+<=1 and how does the solver knows not use any of the wall function method.

Thanks in advance

April 18, 2012, 04:15	Low Re Mesh	#1
naveen_010 New Member vishnu Join Date: Feb 2011 Posts: 8 Rep Power: 15	Dear CFD users In low Re number modelling how does the solver knows, to solve governing equations in all the cells including near wall cells and not to use wall function. I am defining Low Re number k-e turb model with inlet and pressure boundary condition along with standard wall function. For your information the near wall cells follows the Y+ = 1 and I am having around 12 layers of mesh near the wall. Thanks in advance.

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April 18, 2012, 04:38		#2
aerospaceman Member Join Date: Nov 2009 Posts: 43 Rep Power: 16	Hi, As I understand it, you have to select (or not) a solver setting that will employ wall functions. You are then forcing the code to resolve the boundary layer as opposed of modelling. That is "how it knows.." Look up your Theory/Users Guide for the package you are using. Generally however, I'd refine the grid more in order to ensure that everywhere in your domain your Y+ is less than one. Now don't confuse "Wall Function" with "Wall Damping Functions". Hope this helps.

April 18, 2012, 09:40		#3
naveen_010 New Member vishnu Join Date: Feb 2011 Posts: 8 Rep Power: 15	Dear Aerospaceman I am using star-cd and in the panel I can choose either stanard wall function,Non-equillbrium or Angelberger for wall function and there is no option to deselect or make it off. with this if i am using a mesh with y+<=1 and how does the solver knows not use any of the wall function method. Thanks in advance